Field of the Invention
The invention relates to a cement production plant having a preheater for preheating cement raw meal, a calciner for precalcining the preheated cement raw meal and a rotary tube furnace for firing the precalcined cement raw meal, wherein the calciner has a riser tube line through which the exhaust gases from the rotary tube furnace flow and which has a calciner nozzle.
Description of Related Art
Tremendous amounts of fuel are necessary for cement production. Efforts are therefore made to optimize the combustion process by, inter alia, analyzing the composition of the furnace exhaust gases and taking this into account in controlling the combustion process. In this way, it is possible to avoid dangerous operating conditions, reduce pollutants and improve the product quality. Protection against caked material is also an important point. The taking off of the gas was in the past and is sometimes also today carried out via long, water-cooled lances which are pushed from the side into the furnace inlet housing and project to before the furnace inlet seal. Although this is still the best position from a process engineering point of view, the lances are there subjected to high wear because of the ever higher thermal stress and the increased use of secondary fuels, so that the availability becomes ever lower and the maintenance requirements become ever higher. A change has therefore been made to carry out the measurements in the gas line adjoining the furnace inlet housing.
In WO 2010/049836 A1, the gas is taken off in the lower region of the riser tube line of the calciner. For this purpose, the gas is fed to a gas analysis instrument via a gas offtake port which is joined flush to the riser tube line. Although the wear is significantly lower compared to the lances projecting to the riser tube line as a result of the flush arrangement, it has also been found that a significantly greater measurement accuracy has to be accepted here.
DE 299 24 941 U1 relates to a plant for carrying out a process for firing pulverulent raw material, which has a cyclone preheater, a calciner, a furnace and a cooler, with an analytical measuring instrument for the process gases being arranged in the connecting line between furnace and calciner. Furthermore, DE 10 2008 036 088 B4 describes a process for operating a cement plant having a preheating zone, calcination zone and sintering zone, with a gas analysis being carried out in the inlet region of the sintering zone, the calcination zone and/or upstream of the beginning of the preheating zone.